Why is a child born in northwest Los Angeles four times as likely to be diagnosed with autism as a child born elsewhere in California?
Medical experts have pondered for years why autism rates have soared nationwide, and why the disorder appears to be much more prevalent in certain communities than in others. Now, some recent studies that zero in on California may shed some light on these baffling questions.
Researchers from Columbia University, in a study published in the current Journal of Health & Place, identified an area including West Hollywood, Beverly Hills and some less posh neighborhoods that accounted for 3% of the state's new cases of autism every year from 1993 to 2001, even though it had only 1% of the population.
Another recent study, from the University of California, Davis, published in Autism Research, also found high rates of autism in children born around Los Angeles, as well as nine other California locations. Autism, usually diagnosed before a child is 3 years old, is a developmental disorder characterized by impaired social interaction and communication and repetitive behavior.
Both of the California-based studies suggest that local environmental or social factors are driving the high autism-diagnosis rates. And they conclude that childhood vaccinations—which some people fear is a factor behind rising autism—are not to blame. Otherwise, diagnoses of the disorder would be more evenly dispersed, they say.
The studies also disagree on some points. According to the UC Davis study, greater concentrations of autism occur in communities where parents are highly educated, which could mean they have more awareness of autism and access to treatment. By contrast, the Columbia researchers discount the role of educational levels. They believe that social influences, such as shared information about diagnoses, doctors and services, are largely responsible for the high rates they found in parts of Los Angeles.
In Los Angeles itself, residents have a variety of explanations for the high autism rates, ranging from a family's affluence and the activity of autism-advocacy groups to past air and water pollution.
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On average, one in 110 American 8-year-olds had an autism spectrum disorder in 2006, an increase of 57% since 2002, according to a December report from the Centers for Disease Control and Prevention. Some parts of the U.S. are seeing much higher rates than others: Metropolitan Phoenix, for example, has twice the prevalence as northern Alabama.
Whether those differences reflect actual higher risk in different regions, differences in awareness among local residents, or simply variations in record keeping is something the CDC is trying to untangle.
"We still don't know what causes autism, and we don't know a lot of the underlying factors, so we can't rule out the possibility that there are differences in the distribution of risk factors." says Jon Bai, a CDC epidemiologist.
Theories abound to explain the steep increase that has occurred in recent years. Some experts attribute it to genetic changes within families. But others say genetic changes wouldn't occur so quickly and instead they blame environmental toxins or childhood vaccinations.
HT: Bill J.